Description

Giardiasis* is an intestinal infection in dogs caused by the protozoa Giardia lamblia. The most common symptom is diarrhea. The zoonotic potential of giardiasis is controversial.

Symptoms

A range of clinical syndromes may occur, with gastrointestinal syndromes being the most prevalent.

Gastrointestinal

A small number of infected individuals experience an abrupt onset of abdominal cramps, explosive, watery diarrhea, vomiting, foul flatus, and fever which may last for 3–4 days before proceeding into a more sub-acute phase. The majority of infected persons develop gradual symptoms that become recurrent or resistant.

In both the acute and insidious onsets of symptoms, stools become greasy and malodorous but do not contain blood or pus because giardiasis does not involve dysenteric symptoms. Watery diarrhea may cycle with soft stools and constipation. Upper GI symptoms including nausea, early satiety, bloating, substernal burning, egg-smelling halitosis, and acid indigestion may be exacerbated by eating and are generally present in the absence of soft stools.

Constitutional

The most common constitutional symptoms are anorexia, malaise, and fatigue. Weight loss affects more than 50% of patients. Adults with long lasting malabsorption syndrome and children with failure to thrive may experience chronic illness.

Additional syndromes may include lactose intolerance and allergic manifestations such as erythema multiforme, bronchospasm, biliary tract disease, and urticaria.

Physical

Abdominal examination may expose nonspecific tenderness even if there is no sign of peritoneal irritation. Rectal examination should expose heme-negative stools and in severe cases, there may be evidence of dehydration.

Diagnosis

Giardiasis is typically diagnosed by stool ova and parasites (commonly called O&P).

It may be found on duodenal biopsies and is in the differential diagnosis of celiac disease.

Treatment

First line of treatment

Metronidazole (Flagyl)

Adult dosage: 250 mg three times a day for 5 days

Pediatric dosage: 15 mg per kilogram of body weight per dose, 3 times per day, for 5 days

Side effects: Found in 7.1% of cases.  Include unpleasant metallic taste which might cause noncompliance in patients, GI discomfort such as vomiting, nausea, diarrhea, abdominal cramps, pancreatitis, vertigo, headache, CNS toxicity, transient leukemia, dizziness, drowsiness, lassitude, paraethesias, urticaria, and pruritis.  It causes mutation in salmonella and induces tumor in rodents, but mutagenicity has never been observed in humans.

Contraindication: Avoid alcohol while taking metronidazole. Metronidazole causes severe vomiting, headache, and GI discomfort by inhibiting aldehyde dehydrogenase, which breaks down alcohol.

Additional drug facts: Metronidazole is a member of the family of nitroimidazoles, commercially known as Flagyl.  The tablets are quickly and completely absorbed by the small intestine and found to have antigiardial effects on the trophozoites both in vivo and in vitro.  However, it is ineffective against cysts.  The drug is able to penetrate body tissues and could be found in saliva, breast milk, semen, and vaginal fluid.  It is metabolized in liver and secreted in urine.  Metronidazole targets trophozoites by forming active metabolites, which selectively inhibit DNA segregation in anaerobic protozoa such as giardia by DNA breakage and cross-linking.  It has minimal effects on host cells lining the intestinal lumen. Resistance is induced in laboratory and is correlated with decreased activity of parasite pyruvate.

Tinidazole (Fasigyn)

Adult dosage: 2 g once

Pediatric dosage: 50 mg per kilogram of body weight once (max. 2 g)

Side effects: Side effects similar to metronidazole  but appears to be better tolerated and just as effective.  Common side effects include bitter taste, vertigo, and GI discomfort.  The drug should be taken with food to minimize side effects.

Additional drug facts: Tinidazole was FDA approved. It is another member of the nitro-imidazole family. Health care providers recommend travelers (especially those traveling to Asian countries) buy the drug at the country of their destination and take it in an event of giardia infection.  The drug tablets can also be crushed and mixed with cherry syrup (Humco and others) for children. The syrup suspension can be kept at room temperature for 7 days and should be shaken before use.

Nitazoxanide

Adult dosage: 500 mg two times a day for 3 days

Pediatric dosage: 1–3 yrs: 100 mg every 12 hours for 3 days; 4–11 yrs: 200 mg every 12 hours for 3 days

Side effects: A variety of side effects were reported but they occurred infrequently in all studies.  Studies failed to provide sufficiently similar results for a comprehensive analysis of the side effects of nitaxonzanide.  Some probable adverse effects include abdominal pain, dyspepsia, constipation, yellow discoloration of urine, dysuria and dry mouth, and dizziness.  The drug should be taken with food to minimize adverse effects.

Additional drug facts: Nitazonxanide is FDA-approved as an oral suspension for treatment of giardiasis. It can be purchased in 500 mg tablets and in oral suspension.

Wikipedia and GNU

The content of this entry is from the Wikipedia article "Giardiasis" licensed under the GNU Free Documentation License.